This article was posted at Ed Felten's Freedom to Tinker Blog and is reposted here with permission of the author.

I wrote yesterday about discrepancies in the results reported by Sequoia AVC Advantage voting machines in New Jersey.

Sequoia issued a memo giving their explanation for what might have happened. Here’s the relevant part:

During a primary election, the “option switches” on the operator panel must be used to activate the voting machine. The operator panel has a total of 12 buttons numbered 1 through 12. Each party participating in the primary election is assigned one of the option switch buttons. The poll worker presses a party option switch button based on the voter authorization slip given to the voter after signing the poll book, and then the poll worker presses the green “Activate” button. This action causes that party’s contests to be activated on the ballot face inside the voting booth.

Let’s assume the Democrat party is assigned option switch 6 while the Republican Party is assigned options switch 12. If a Democrat voter arrives, the poll worker presses the “6″ button followed by the green “Activate” button. The Democrat contests are activated and the voter votes the ballot. For a Republican voter, the poll worker presses the “12″ button followed by the green “Activate” button, which then activates the Republican contests and the voter votes the ballot. This is the correct and proper method of machine activation when using option switches.

However, we have found that when a poll worker selects the lower of the
two assigned selection codes, followed by pressing an unused selection
code and then pressing the green “Activate” button, the higher numbered
party on the operator panel has its contests activated instead while
the selection code button for the original party stays active on the
operator panel.

Using the above example with the Democrat Party as option switch 6 and
the Republican Party as option switch 12, the poll worker presses
button 6 for Democrat. The red light next to button number 6 lights up
and the operator panel display will show DEM. The poll worker then
presses any unused option switch. The red light stays lit next to
option switch 6 and the display still says DEM. Now the poll worker
presses the green “Activate” button. The red light stays lit next to
button number 6, but the operator panel display now says REP and the
ballot in the voting booth will activate the Republican party contests.

In each and every case where a machine displays the party turnout issue
at the close of the polls, this is the situation that would have caused
it, and it can be duplicated on any machine. In addition, for this
situation to have occurred, the voter that was in the voting booth at
the time of the poll workers action would have voted the opposite party
ballot instead of telling the poll worker that the incorrect ballot was
activated and the machine would not allow them to vote the party they
intended. If they had informed the poll worker, they could have made
the party selection change and the voter would have then voted the
correct ballot style.

Several points are in order.

First, it’s obvious from this description, and from the fact that this
happened on so many machines across the state, that even if Sequoia’s
explanation is entirely correct, there was some kind of engineering
error on Sequoia’s part that caused the machines to misbehave. Sequoia
has tried to paint the anomalies as poll worker error, but that’s not
plausible in light of Sequoia’s own explanation.

Consider the scenario described above: there is a moment when the red
light next to the DEM button is lit, the operator panel displays DEM,
then the poll worker presses the Activate button — and the Republican
ballot is activated. No sane engineer would design a system to work
that way.

No sane engineer would design this system to ever display REP in the
operator panel while simultaneously lighting only the DEM light.

No sane engineer would design this system to ever activate the
Republican ballot when the poll worker had pressed the DEM button but
had not pressed the REP button.

Sequoia’s own explanation makes clear that they made an engineering error that caused the voting machine to behave incorrectly.

Second, this doesn’t look like fraud, only error. A malicious attacker
who had access to a machine would have had much more powerful, and much
less detectable, options at his disposal.

Third, Sequoia seems to avoid saying that what they describe is the
only possible cause of such errors. Note the careful wording, “In each
and every case where a machine displays [an error], this is the
situation that would have caused it …” (emphasis added). They don’t say
this “did” cause the errors; they say it “would have”. The sentence is
either clumsy or artfully worded.

Fourth, Sequoia’s explanation involves a voter seeing the wrong party’s
ballot being activated, and not complaining about it. Assuming (as
press accounts say) that the problem happened about sixty times in New
Jersey, one would expect that many voters noticed and complained. And
one would expect that in at least one of those cases, a poll worker
would have noticed that the operator panel was displaying REP and DEM
at the same time. Yet there don’t seem to be reports of such behavior.

Fifth, Sequoia doesn’t characterize fully the cases where this problem
might occur, so election officials don’t know, for example, which past
elections might have been affected.

The bottom line is clear. An investigation is needed — an independent
investigation, done by someone not chosen by Sequoia, not paid by
Sequoia, and not reporting to Sequoia.